Thursday, April 29, 2010

Western Disturbance to lessen Heat,Temporarily:
With a moderate precipitating rains/duststorms in Pakistan, I see the system crossing over into India by the 30th.

Result: Fairly good rains/hailstorms in the North-West/North and Central regions of India.
And with some rain in South Vidharbh today (29th.), the scorching heat of Vidharbh now underway, will lessen with the passing of the W.D. from tomorrow.
Expect the highs in Vidharbh to come down from 45c to 41/42c.Since the W.D. is moderately strong, the days will surely get cooler by 3/4c starting 30th. North Indian states, Gujarat and baking in intense 43/45c temperatures, can expect some relief,albiet for a few days only.
Today, the highest in Asia was 45c at Nagpur (India) and Nawabshah(Pakistan).
All this relief is temporary for a couple of days, till the passing of the W.D. The heat is immiediately following up in the rear of the system.
Mumbai was a sweaty 35.5c (+3c), and cloudless.(Though I was expecting some clouding today). Mahableshwar couln't be any better too, as the day was hot today at 33c with no relief at night,20c. Thane, too was scorching at 38.8c (AWS reading).

Monsoon Watch - 4

The parameter of utmost concern to me now is the Bay factor. The consistently -ve factor in the first 3 MWs.
The latest winds in the Bay show a strong current rushing Northwards along the East coast of India, into the trough in sub-Himalayan West Bengal. The North-West flow of winds into the Myanmar coast also exists. Thereby, to some extent, the hitherto prevailing "high" is somewhat breaking up.
Also, the SST in the Bay is quite conducive to host a low anytime now. Like previously mentioned, a low, according to me, should have normally formed by 15th.April.Infact,last year we had a cyclone in the Bay in April.A delay here can effect the Bay branch of the Monsoon. Now, the delay in the formatiion of the wanted low is due to the trough running along the North-Eastern states, which has caused very heavy rains there. Moisture laden winds are gushing into the region, causing heavy rains.
Now, according to ECMWF forecasts, and other models,no low is predicted in the Bay till the 6th.May at least. Indicator :-ve

The Seasonal Low in the Thar Desert is deepening gradually. As on end April, a pressure of 1000 mb in the central core region around Barmer is normal.(See Thai Met Dept Map). Now onwards,the core should expand, and stretch into the West, into Pakistan, and within a week further West. Finally, by June, the low has to stretch from India to Arabia, with its core centre (994mb) somewhere near Jacobabad. The intense heat in the sub continent is an useful aide to this formation.
Also, further heavy moisture inflow from the North-West winds into Kerala and South Karnataka coast may prevent a proper gradiant to form to give the Monsoon a final momentum and push along the west coast. During end of May,the low in the North (Rajasthan/Sindh) may be normal at 996mb,but the 1008 mb required off the Southern tip may not materise on time. And that is a must for creating a pull Northwards for the Monsoon.Still, we have the month of May for the situation to "cool off", or rather "warm up" along the south- west coast. Indicator :Normal.

Another parameter to observe now are the 200 hpa jet stream. Normally, they should be Easterlies right upto 20N by May end. This would facilitate the Northward movement of the Monsoon Current. Today, the jet stream is developed upto the Equator, and are gaining strenght over Sri Lanka.(See COLA/IGES Map) Forecasts on models show these winds getting organised around the first week of May. Should march up to the 10N by middle of May, to be in time for the Andaman Sea Monsoon arrival. Indicator: Normal

The cross equatorial flow, is surely picking up. A very crucial factor this one. The Mascrene highs are establishing and winds hitting the East African coast are getting stronger, and the Somali Current is getting defined. The lacking factor is the cross flow south of the Bay, that is, the Eastern parameter.(See Aust. Bur. of Met.TXLAPS Wind chart attached). The Bay branch should be getting stronger by now, but lacks the momento. But, a push is there in the offing. As reported by the Australian Weather buraeu "The latest guidance suggests that an active MJO event will develop in the western Indian Ocean over the coming week or two. In response to this, we would expect to see an increase in convective activity over the northern Indian Ocean, although is unlikely to trigger the Indian Monsoon onset this early in the year."
However, I feel, this will be a good booster for the Bay branch of the Monsoon. Remember, the due date for the Monsoon in the South Andaman Sea is May 12th. Indicator: Normal.

The cyclone in the Southern Indian Ocean has dissipitated, hence there is no longer any hindrance now for the ITCZ to start moving North. Situated at 5S, it should normally cross the equator around 10th.May,for a proper setting of the Monsoon in both the branches.
El-Nino: According to the latest report from the Australian Weather Bureau, "the majority of ENSO indicators have now dropped below El Niño thresholds. The cooling of the tropical Pacific Ocean ..has resulted in trade winds and tropical cloudiness returning to normal."
But, my estimates show that a weak El-Nino is still hanging around.
Regions Previous Current Temperature change
(2 weeks)
Nino 3         0.3°C cooler
Nino 3.4     0.1°C cooler
Nino 4        0.1°C cooler
While checking out all the other parameters, we cannot neglect this very important event. Still, as we have time in hand, and if all goes well, SST can start declining , and come to neutral levels by May end. SOI indicates this favourably, as it is now gained a few notches up to +15 on April 25th.. Very very encouraging. In fact,sustained positive values of the SOI above +10 may indicate La Niña episodes.
Indicator: +ve

Really, we are still at the mercy of Nature and Providence in spite of our so called "developments."

Conclusion: As of today, there seems to be a slight delay in the Bay branch of the Monsoon. And, the Arabian Sea branch needs a little trigger to get going in May. Maybe a little less rain in the first half of May for Kerala? Arrival date should be around 1st. June for Kerala.
(This Monsoon chase is my personal deciphering).
@rohitweet >> Is it raining there now ?? Please update. Thanks... Check the satellite shot at 7pm ..
RT @MiLOKMAT: Nagpur: Rains occurred at Chandrapur-Ballarshah region while the sky was overcast in the city and many other parts as well.
RT @nikhil_nine: wow...Garwa..@rohitweet Unexpected change in weather. It may rain here in Nagpur
RT @MiLOKMAT: Nagpur: Parts of South-Vidarbha today received showers which brought much needed relief to the people in the region. ... South central Bay is dotted with thunder cells and getting ready to host a minor low level circulation.
7pm, Heavy showers over East Maharastra, N. Karnataka, WEst central Tamilnadu along W.Ghats and N-W Srilanka..
RT @ESIPAQWG: RT @khurafatinitin Delhi is headed for a dust storm and squall ! Hopefully it shall rain heavily !
7pm, Today's thunder showers over most parts are still persisting .. Very heavy over pakistan...
RT @barkhad: Hail stones! Rain! Delhi! Seriously!!!!!!
RT @SachdevCharu: Love April showers in Delhi! Love the smell of soil when rain falls on scorching land.
6pm, Showers over S. Kerala western ghats ..
6pm, Heavy showers along North A.P into East Maharastra ..
RT @AlertNet: Slideshow of photos from AlertNet's George Fominyen, who's been reporting on hunger in Niger
4:30pm, More showers pushing into w-N-W Rajasthan from Pakistan ..
RT @munnartravel: kerala photo gallery , munnar photos ..
@Biorahul >> Yes, there are lots of chances for showers in Jaipur and most of central and N-W Rajasthan.
RT @mj12889: clouds over delhi................... rain rain come again
RT @akashkumarsingh: @weatherofindia yes now 29 apr 5pm , it s raining in delhi
@Biorahul >> Any rain in Jaipur today ?
@bbyf16 >> Is it raining in Kerala? Where are you updating from ? Thanks.
3pm, Showers over N-W Rajasthan, N Andhra into Maharastra .. isolated over Kerala w.Ghats, S.Karnataka and S.Tamilnadu..
From reader >> "Very dark and cloudy in Virudhunagar..expecting suuuper shower:-)"
2:30pm, Thunder cells over Munnar & Kodaikanal mountains and over Ramnad dist. of Tamilnadu ..
Low level circulation over S-central bay, this will increase the Shower possibility along TN coast from 1-May...
A minor low level Cyclonic circulation predicted over South-Central Bay on 1-May...
1pm, Thunder cells visible over central Pakistan and over N-W Rajasthan, heavy showers continue over South N-E states ..
Chennai - touched another moderate temp of 35.1°C (12:14pm). Now 12:23pm, the morning cloud formation has not sustained again.
Chennai - At 11:30am, minor thunder cells over to East and South-east over Sea. A sign of new weather front moving into N Tamilnadu coast .
Chennai - From 8am till 11:30am sky was having a DEEP blue color (sign of new weather front) and littered with lots of LOW cloud formation.
Early morning, Massive showers over N-E states .. and signs of showers over west-central Rajasthan ..
RT @rajugana: Hyd-downpour yesterday evening., Baroda- Hot and humid..clear signs of even development of clouds... (28-Apr-10)
Thunder squalls likely in east, north-east ...

Thunder squalls likely in east, north-east

India Meteorological Department (IMD) on Wednesday warned about the possibility of isolated thunder squall over the north-eastern States, West Bengal, Sikkim, Bihar, Jharkhand and Orissa, apart from Kerala in the South, during the next two days.

Weather over north-west India would also stay largely unstable with isolated hailstorms or thunder squall forecast over Punjab, Haryana, Delhi, Chandigarh, Rajasthan, Uttar Pradesh and Madhya Pradesh during this period.


The volatile weather is being brought to bear by the causative trough formations spearheaded by embedded cyclonic circulations at all these places.

The IMD on Wednesday traced the most prominent among them running north to south trough from Gangetic West Bengal to Kerala across Orissa, Andhra Pradesh and Karnataka. Embedded upper air cyclonic circulations sat over Gangetic West Bengal and adjoining Jharkhand.

A second trough originating from Gangetic West Bengal headed eastward to Mizoram across Bangladesh and Tripura with an embedded upper air cyclonic circulation over Mizoram. These trough formations in the eastern corridor have seen oodles of moisture being washed inland from the Bay of Bengal in the lower levels of the atmosphere.

Meanwhile, a cyclonic circulation induced by an inbound western disturbance traced to over central Pakistan on Tuesday has moved further east, partly across the international border, to lie over central Pakistan and adjoining northwest Rajasthan. This is seen as stirring up a lot of weather over northwest India in isolated hail storms and thunder squalls extending into as far east as Uttar Pradesh and east-southeast into Madhya Pradesh as well.


The IMD stated on Wednesday that the western disturbance is affecting western Himalayas and would stay active over the region during the next two to three days.

Satellite imagery on Wednesday morning showed the presence of convective (thunderstorm/thundershower-causing) clouds over parts of Jammu and Kashmir, south Bay of Bengal and south east Arabian Sea.

Low to medium clouds (partly clouded conditions) were witnessed over Himachal Pradesh, Punjab, west Haryana, west Uttar Pradesh, north Rajasthan, east Madhya Pradesh, Chhattisgarh, Orissa, south peninsular India, south Andaman Sea and remaining parts of south Arabian Sea.

The cloud cover is expected to bring about a fall in maximum temperatures by 2-3 deg Celsius over northwest and adjoining central India during the next two days.

The European Centre for Medium-Range Weather Forecasting (ECMWF) is of the view that northwest and central India would start heating up once again once the effect of the western disturbance wears out.

The US National Centres for Environmental Prediction (NCEP) is of the view that rain or thundershowers over northeast India and the southwest coast would continue into the second week of May.

An IMD outlook until Saturday said that scattered to fairly widespread rain or thundershowers would occur over Assam, Meghalaya, Arunachal Pradesh, Nagaland, Manipur, Mizoram and Tripura.

Scattered rain or thundershowers are also likely over Jammu and Kashmir, Himachal Pradesh and Uttarakhand.

Isolated dust storm or thunderstorms have been forecast over Punjab, Haryana, Delhi, Chandigarh, Rajasthan, Uttar Pradesh, north Madhya Pradesh and Chhattisgarh during the next two days.

Isolated to scattered rain or thundershowers would occur over West Bengal, Sikkim, Bihar, Jharkhand and Orissa. Isolated rain or thunder showers are likely over Maharashtra.

Isolated to scattered rain or thundershowers has been forecast over Andhra Pradesh, Karnataka, Tamil Nadu, Kerala, Lakshadweep and Andaman and Nicobar Islands.

Forecast until Monday said that fairly widespread rainfall activity would occur over the north eastern States while it would be isolated over east and south peninsular India.

Severe heat wave conditions have been prevailing over isolated pockets of Himachal Pradesh during the last 24 hours ending Wednesday morning.

Heat wave conditions prevailed over parts of Haryana, west Uttar Pradesh and Rajasthan and isolated pockets of Punjab, north-west Madhya Pradesh and Jharkhand. The highest maximum temperature of 45.5 deg Celsius was recorded at Jhansi in Uttar Pradesh.